Laser Projector with Improved Efficiency

ABSTRACT

A laser projector includes a light combining device, a light splitting system, a plurality of light valves, and a beam combiner. The light combining device is for emitting an illumination beam. The light splitting system is for receiving the illumination beam to generate a plurality of color beams. The plurality of light valves is for receiving and modulating the plurality of color beams to generate modulated color beams. The beam combiner is for combining the modulated color beams to form a multi-color image.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention is related to a laser projector, in particular toa laser projector that can reduce optical elements and improveefficiency.

2. Description of the Prior Art

Projection systems require a high quality light source. While projectionsystems have traditionally used discharge lamps as a light source, thereis now interest in alternative light sources such as lasers. Lasers haveseveral advantageous properties. They emit a high intensity light beamand have a very long operating lifetime.

However, laser projectors generally use blue light laser sources asillumination beams. The illumination beam needs to be converted intobeams of other colors by a wavelength conversion device (such as a colorwheel partially coated with phosphor or quantum dots), and then combinedwith the original illumination beam to be the projector light source.The traditional light combining module uses a light splitting system toreflect the illumination beam and then projecting it to the color wheel.The color wheel includes a wavelength conversion material to generate anexcited light beam which can directly penetrate the light splittingsystem. In addition, part of the illumination beam passes through thepart of the color wheel without wavelength conversion material, andreturns to the beam splitter through a plurality of reflectors. Theillumination beam is then reflected by the beam splitter to combine withthe excited light beam. The traditional light combining module needs tobe equipped with many optical components, which not only greatly add tothe hardware cost, but also add to the weight and volume of the product.

SUMMARY OF THE INVENTION

An embodiment provides a laser projector including a light combiningdevice, a light splitting system, a plurality of light valves, and abeam combiner. The light combining device includes a laser light source,a dichroic mirror, a reflecting mirror, and a wavelength converter. Thelaser light source is for providing a first light beam on a firstoptical path. The dichroic mirror has a first surface and a secondsurface and is disposed on the first optical path between the laserlight source and the reflecting mirror. The first surface reflects afirst portion of the first light beam. The second surface reflects asecond portion of the first light beam to a second optical path. Thereflecting mirror is disposed on the first optical path and is forreflecting the second portion of the first light beam to the secondsurface of the dichroic mirror. The wavelength converter is forreceiving the first portion of the first light beam reflected from thefirst surface and emitting a second light beam to the second opticalpath. The second portion of the first light beam and the second lightbeam form the illumination beam on the second optical path. The lightcombining device is for emitting an illumination beam. The lightsplitting system is disposed on the second optical path for receivingthe illumination beam to generate a plurality of color beams. Theplurality of light valves is for receiving and modulating the pluralityof color beams to generate modulated color beams. The beam combiner isfor combining the modulated color beams to form a multi-color image.

Another embodiment provides a laser projector including a lightcombining device, a light splitting system, a plurality of light valves,and a beam combiner. The light combining device includes a laser lightsource, a dichroic mirror, a reflecting mirror, and a wavelengthconverter. The laser light source is for providing a first light beam ona first optical path. The dichroic mirror has a first surface and asecond surface and is disposed on the first optical path between thelaser light source and the reflecting mirror. The first surface reflectsa first portion of the first light beam. The second surface reflects asecond portion of the first light beam to a second optical path. Thesecond portion of the first light beam penetrates the dichroic mirror.The reflecting mirror is disposed on the first optical path and is forreflecting the second portion of the first light beam to the secondsurface of the dichroic mirror. The wavelength converter is forreceiving the first portion of the first light beam reflected from thefirst surface and emitting a second light beam to the second opticalpath. The second light beam penetrates the dichroic mirror. The secondportion of the first light beam and the second light beam form theillumination beam on the second optical path. The light combining deviceis for emitting an illumination beam. The light splitting system isdisposed on the second optical path for receiving the illumination beamto generate a plurality of color beams. The plurality of light valves isfor receiving and modulating the plurality of color beams to generatemodulated color beams. The beam combiner is for combining the modulatedcolor beams to form a multi-color image.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a laser projector of an embodiment of the presentinvention.

FIG. 2 is a diagram of the light combining device of FIG. 1.

FIG. 3 is a diagram of the wavelength converter in FIG. 2.

FIG. 4 is a diagram of another embodiment of the light combining devicein FIG. 1.

FIG. 5 is a diagram of the wavelength versus the transmittance of thedichroic mirror in FIGS. 2 and 4.

DETAILED DESCRIPTION

FIG. 1 is a diagram of a laser projector 100 of an embodiment of thepresent invention. The laser projector 100 includes a light combiningdevice 10, a light splitting system 20, a plurality of light valves 32,34, 36, and a beam combiner 40. The light combining device 10 is foremitting an illumination beam WL. The light splitting system 20 is forreceiving the illumination beam WL to generate a plurality of colorbeams, including a blue light beam BL, a yellow light beam YL, a greenlight beam GL, and a red light beam RL. The first light valve 32receives and modulates the blue light beam BL. The second light valve 34receives and modulates the green light beam GL. The third light valve 36receives and modulates the red light beam RL. The light combiner 40 isfor combining the modulated blue light beam BL, green light beam GL, andred light beam RL to form a multi-color image. The light splittingsystem 20 includes a polarization conversion system PCS to convert theillumination beam WL into a polarized beam WPL. The light splittingsystem 20 also includes a first dichroic mirror 22, a second dichroicmirror 24, a first reflecting mirror 26, a second reflecting mirror 27and a third reflecting mirror 28. The light splitting system 20 is forconverting the polarized beam WPL to the plurality of color beams andguiding them to the corresponding light valves.

In other words, the optical path of the laser projector 100 of theembodiment can be described as follows. The light combining device 10emits the illumination beam WL to the polarization conversion systemPCS, and the polarization conversion system PCS converts theillumination beam WL to the polarized beam WPL. The polarized beam WPLis then directed to the first dichroic mirror 22. The first dichroicmirror 22 separates the polarized beam WPL into the blue light beam BLand the yellow light beam YL, and guides the yellow light beam YL to thesecond dichroic mirror 24 and the blue light beam BL to the firstreflecting mirror 26. The first reflecting mirror 26 reflects the bluelight beam BL to the light valve 32. The second dichroic mirror 24receives and separates the yellow light beam YL into the green lightbeam GL and the red light beam RL. The second dichroic mirror 24reflects the green light beam GL to the second light valve 34. The redlight beam RL is reflected sequentially by the second mirror 27 and thethird mirror 28 to the third light valve 36. The blue light beam BL, thegreen light beam GL and the red light beam RL are modulated respectivelyby the first light valve 32, the second light valve 34 and the thirdlight valve 36. After modulation, each beam is respectively guided tothe light combiner 40 and combined to form a multi-color image.

FIG. 2 is a diagram of the light combining device 10 of FIG. 1. Thelight combining device 10 includes a laser light source 12, a dichroicmirror 14, a reflecting mirror 16, and a wavelength converter 18. Thelaser light source 12 is for providing the first light beam L1 on thefirst optical path OP1. The dichroic mirror 14 has a first surface S1and a second surface S2. The dichroic mirror 14 is disposed on the firstoptical path OP1 between the laser light source 12 and the reflectingmirror 16. The first surface S1 reflects the first portion L11 of thefirst light beam L1. The reflecting mirror 16 is disposed on the firstoptical path OP1. The second portion L12 of the first light beam L1 canbe reflected by the reflecting mirror 16 to the second surface S2 of thedichroic mirror 14. The second surface S2 then reflects the secondportion L12 of the first light beam L1 to the second optical path OP2.The wavelength converter 18 is for receiving the first portion L11 ofthe first light beam L1 reflected from the first surface S1 andgenerating the second light beam L2 to the second light path OP2. Thesecond portion L12 of the first light beam L1 and the second light beamL2 are combined to form the illumination beam WL on the second opticalpath OP2. The first light beam L1 can be blue light with a wavelengthrange from 450 to 475 nm, and the second light beam L2 can be yellowlight with a wavelength range from 570 to 590 nm. The dichroic mirror 14can have different transmittances for light of different wavelengths.The first optical path OP1 may be perpendicular to the second opticalpath OP2, and the angle between the dichroic mirror 14 and the firstoptical path OP1 may be 45 degrees. This configuration can reduce thelens and other optical elements required by the projector, thereforeimproving optical efficiency.

In other words, the optical path of the light combining device 10 isdescribed as follows. The laser light source 12 emits the first lightbeam L1 to the first optical path OP1. The first portion L11 of thefirst light beam L1 is projected on the first surface S1 of the dichroicmirror 14 and is reflected to the wavelength converter 18. Thewavelength converter 18 receives the first portion L11 of the firstlight beam L1 and generates the second light beam L2 to the second lightpath OP2. The second light beam L2 then penetrates the dichroic mirror14. The second portion L12 of the first light beam L1 bypasses thedichroic mirror 14 and is reflected by the reflecting mirror 16 to thesecond surface S2 of the dichroic mirror 14. The second surface S2 thenreflects the second portion L12 of the first light beam L1 to the secondoptical path OP2. The second portion L12 of the first light beam L1 andthe second light beam L2 are combined to form the illumination beam WL.The illumination beam WL is then emitted out of the light combiningdevice 10 to be the source illumination beam of the laser projector 100.

FIG. 3 is a diagram of the wavelength converter 18 in FIG. 2. Thewavelength converter 18 has a reflective substrate 62. The wavelengthconversion coating 66 is coated on the substrate 62 to receive the firstportion L11 of the first light beam L1 to generate the second light beamL2. For example, the wavelength conversion coating 66 may be phosphor orquantum dots, which can absorb blue light and generate yellow light byluminescence excitation. In this embodiment, the wavelength converter 18is a rotatable color wheel, and the disc is made of reflective material.The wavelength conversion coating 66 is a ring-shaped region on thereflective substrate. When the first portion L11 of the first light beamL1 is projected on point P of the high-speed rotating wavelengthconverter 18, the wavelength conversion coating 66 can be excited togenerate the second light beam L2 to the second optical path OP2. Thewavelength conversion coating 66 can be consumed uniformly by rotatingthe wavelength converter 18 at a high speed. Through the aforementionedoptical mechanism, the second portion L12 of the first light beam L1 andthe excited second light beam L2 can be combined to form theillumination beam WL.

FIG. 4 is a diagram of another embodiment of the light combining device10 in FIG. 1. The light combining device 10 includes a laser lightsource 12, a dichroic mirror 14, a reflecting mirror 16, and awavelength converter 18. The laser light source 12 is used to providethe first light beam L1 on the first optical path OP1. The positionarrangement of the dichroic mirror 14 and the reflecting mirror 16 inFIG. 4 is different from that in FIG. 2. The dichroic mirror 14 has afirst surface S1 and a second surface S2, and is disposed on the firstoptical path OP1 between the laser light source 12 and the reflectingmirror 16. The first surface S1 of the dichroic mirror 14 reflects thefirst portion L11 of the first light beam L1, and the second portion L12of the first light beam L1 penetrates the dichroic mirror 14. Thereflecting mirror 16 is disposed on the first optical path OP1perpendicular to the second portion L12 of the first light beam L1 toreflect the second portion L12 of the first light beam L1 to the secondsurface S2. The second surface S2 then reflects the second portion L12of the first light beam L1 to the second optical path OP2. Thewavelength converter 18 is for receiving the first portion L11 of thefirst light beam L1 reflected from the first surface and generating thesecond light beam L2 to the second light path OP2. The second portionL12 of the first light beam L1 and the second light beam L2 form theillumination beam WL on the second optical path OP2. The first lightbeam L1 can be blue light with a wavelength range from 450 to 475 nm,and the second light beam L2 can be yellow light with a wavelength rangefrom 570 to 590 nm. The dichroic mirror 14 can have differenttransmittances for light of different wavelengths. In addition, thefirst optical path OP1 and the second optical path OP2 may beperpendicular to each other, and the angle between the dichroic mirror14 and the first optical path OP1 may be 45 degrees. This configurationcan reduce the lens and other optical elements required by theprojector, therefore improving optical efficiency.

In other words, the light path of the light combining device 10 can bedescribed as follows. The laser light source 12 emits a first light beamL1 to the first optical path OP1, the first light beam L1 irradiates thefirst surface S1 of the dichroic mirror 14 and the first portion L11 ofthe first light beam L1 is reflected to the wavelength converter 18. Thewavelength converter 18 receives the first portion L11 of the firstlight beam L1 and generates the second light beam L2 to the second lightpath OP2. The second light beam L2 penetrates the dichroic mirror 14.The second portion L12 of the first light beam L1 also penetrates thedichroic mirror 14 and is reflected by the reflecting mirror 16 to thesecond surface S2 of the dichroic mirror 14. The second surface S2 thenreflects the second portion L12 of the first light beam L1 to the secondoptical path OP2. The second portion L12 of the first light beam L1 andthe second light beam L2 are combined to form the illumination beam WL.The illumination beam WL is then emitted out of the light combiningdevice 10 to be the source illumination beam of the laser projector 100.

FIG. 5 is a diagram of the wavelength versus the transmittance of thedichroic mirror 14 in FIG. 2 and FIG. 4. As the diagram shows, thecoating of the dichroic mirror can have almost 100% transmittance forlight with wavelength greater than 500 nm, while only about 20%transmittance for light with wavelength below 450 nm. The transmittanceof light with wavelength from 500 nm to 450 nm gradually decreases inproportion. By implementing this coating characteristic, if the firstlight beam L1 emitted by the laser light source 12 is a blue light withwaveband of 450 nm to 475 nm, a portion of the light beam can penetratethe dichroic mirror 14, and the other portion of the light beam can bereflected by the dichroic mirror 14. If the second light beam L2generated by the wavelength converter 18 is yellow light with wavebandof 570 nm to 590 nm, the second light beam L2 can almost completelypenetrate the dichroic mirror 14. This configuration enables the lightcombining device 10 to combine the blue light beam and the yellow lightbeam to form the source illumination beam for the laser projector 100.

In summary, an embodiment of the present invention provides a laserprojector, which includes a light combining device, a light splittingsystem, a plurality of light valves, and a light combining lens group.The light combining device includes a laser light source, a dichroicmirror, a reflecting mirror, and a wavelength conversion system. Thelaser light source is for providing a first light beam on the firstoptical path. The dichroic mirror is disposed on the optical light pathand has a first surface and a second surface. The first surface of thedichroic mirror can reflect the first portion of the first light beamand the second portion of the first light beam can bypass or penetratethe dichroic mirror. The reflecting mirror is disposed on the firstoptical path and for reflecting the second portion of the first lightbeam to the second surface of the dichroic mirror. The second surfacethen reflects the second portion to the second optical path. Thewavelength conversion system is for receiving the first portion of thefirst light beam reflected from the first surface of the dichroic mirrorand generating the second light beam on the second optical path. Thesecond light beam can bypass or penetrate the dichroic mirror. Thesecond portion of the first light beam and the second light beam formthe illumination beam on the second light path. The light splittingsystem is disposed on the second optical path for receiving theillumination beam to generate a plurality of color beams. The lightvalves receive and modulate the color light beams respectively. Thelight combiner is for combining the modulated color beams to form amulti-color image. The embodiment of the present invention can reducethe lens and other optical elements required by the projector, thereforereducing the hardware cost and reducing the product weight and volume.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A laser projector comprising: a light combiningdevice configured to emit an illumination beam, the light combiningdevice comprising: a laser light source configured to provide a firstlight beam on a first optical path; a dichroic mirror having a firstsurface and a second surface, the dichroic mirror being disposed on thefirst optical path, the first surface reflecting a first portion of thefirst light beam; a reflecting mirror disposed on the first opticalpath, and configured to reflect a second portion of the first light beamto the second surface of the dichroic mirror, the second surface of thedichroic mirror reflecting the second portion to a second optical path;and a wavelength converter configured to receive the first portion ofthe first light beam reflected from the first surface and to emit asecond light beam to the second optical path; wherein: the dichroicmirror is disposed between the laser light source and the reflectingmirror; and the second portion of the first light beam and the secondlight beam form the illumination beam on the second optical path; alight splitting system disposed on the second optical path, andconfigured to receive the illumination beam to generate a plurality ofcolor beams; a plurality of light valves configured to receive andmodulate the plurality of color beams to generate modulated color beams;and a beam combiner configured to combine the modulated color beams toform a multi-color image.
 2. The laser projector of claim 1, wherein thewavelength converter comprises phosphors or quantum dots.
 3. The laserprojector of claim 2, wherein the wavelength converter is rotatable. 4.The laser projector of claim 1, wherein the light splitting systemcomprises a polarization conversion system for converting theillumination beam to a polarized beam.
 5. The laser projector of claim1, wherein the first light beam has a first waveband, the second lightbeam has a second waveband, and the first waveband is different from thesecond waveband.
 6. The laser projector of claim 5, wherein the firstlight beam is a blue light beam and the second light beam is a yellowlight beam.
 7. The laser projector of claim 5, wherein the firstwaveband comprises a first wavelength and a second wavelength differentfrom the first wavelength, and the dichroic mirror allows the firstwavelength to penetrate with a first ratio and the second wavelength topenetrate with a second ratio.
 8. The laser projector of claim 7,wherein the first ratio is the same or different from the second ratio.9. The laser projector of claim 1, wherein the first optical path isperpendicular to the second optical path.
 10. The laser projector ofclaim 1, wherein the dichroic mirror and the first optical pathintersect at a 45 degree angle.
 11. A laser projector comprising: alight combining device configured to emit an illumination beam, thelight combining device comprising: a laser light source configured toprovide a first light beam on a first optical path; a dichroic mirrorhaving a first surface and a second surface, the dichroic mirror beingdisposed on the first optical path, the first surface reflecting a firstportion of the first light beam, a second portion of the first lightbeam penetrating the dichroic mirror; a reflecting mirror disposed onthe first optical path, and configured to reflect the second portion ofthe first light beam to the second surface of the dichroic mirror, thesecond surface of the dichroic mirror reflecting the second portion to asecond optical path; and a wavelength converter configured to receivethe first portion of the first light beam reflected from the firstsurface and to emit a second light beam to the second optical path, thesecond light beam penetrating the dichroic mirror; wherein: the dichroicmirror is disposed between the laser light source and the reflectingmirror; and the second portion of the first light beam and the secondlight beam form the illumination beam on the second optical path; alight splitting system disposed on the second optical path, andconfigured to receive the illumination beam to generate a plurality ofcolor beams; a plurality of light valves configured to receive andmodulate the plurality of color beams to generate modulated color beams;and a beam combiner configured to combine the modulated color beams toform a multi-color image.
 12. The laser projector of claim 11, whereinthe wavelength converter comprises phosphors or quantum dots.
 13. Thelaser projector of claim 12, wherein the wavelength converter isrotatable.
 14. The laser projector of claim 11, wherein the lightsplitting system comprises a polarization conversion system forconverting the illumination beam to a polarized beam.
 15. The laserprojector of claim 11, wherein the first light beam has a firstwaveband, the second light beam has a second waveband, and the firstwaveband is different from the second waveband.
 16. The laser projectorof claim 15, wherein the first light beam is a blue light beam and thesecond light beam is a yellow light beam.
 17. The laser projector ofclaim 15, wherein the first waveband comprises a first wavelength and asecond wavelength different from the first wavelength, and the dichroicmirror allows the first wavelength to penetrate with a first ratio andthe second wavelength to penetrate with a second ratio.
 18. The laserprojector of claim 17, wherein the first ratio is the same or differentfrom the second ratio.
 19. The laser projector of claim 11, wherein thefirst optical path is perpendicular to the second optical path.
 20. Thelaser projector of claim 11, wherein the dichroic mirror and the firstoptical path intersect at a 45 degree angle.